Electrical heater



1934- G. N SEXTON ELECTRICAL HEATER Filed Feb. 20, 1931 2 Sheets-$heet lZSnventor gww . Gttornegd Jan. 2, 1934- a. N. SEXTON 1,941,534

ELECTRICAL HEATER Filed Feb. 20, 1931 2 Sheets-Sheet 2 GttornegAelectrodes; whereas with alternating current Patented jan. 2

UNITED STATES PATENT OFFICE ELECTRICAL HEATER George Norrell Sexton,Richmond, Va. Application February 20, 1931. Serial No. 517,338 M 26Claimsi (01. 219-40) The invention relates to electric heaters, and tosystems for connecting such heaters in circuit.

While the heater here shown may be used for many purposes, it isintended, more particularly, for the heating of water for householdsupply. As here shown, the heater is connected directly in the pipeline, but its use is not limited to this type of connection. l

The heater belongs to that type in which the heat is generated bythepassage of current directly through the fluid while the fluid is flowingthrough the heater, as distinguished from those heaters in which thecurrent passes through some special resistance material from which theheat is transmitted to the fluid by conduction or radiation tojthefluid.

While chemically pure water has a yery high resistance, too high to beheated by current at commercial voltages, the water that is. ordinarilyused for household supply always contains more or less mineral matter inthe form of dissolved salts and other foreign matter; and the presenceof these salts or other substances, even in small quantities, so lowersthe resistance of the water that currentof conunercialvoltages may bereadily used to secure the necessary heat. 7

Moreover the water from any one locality is substantially constant inits dissolved salts. and other foreign matter, .so-that it is practicalto so adjust the heaters for any given locality that they will consumeonly the current necessary to produce the required heat; and when onceadjusted do not ordinarily require to be changed. ,Therefore while theresistance of water of different localities may vary considerably, thefact that it does not vary substantially for any given location makes itpossible to so adjust the heaters that they may be adapted to anyparticular 10-- cality when used as water heaters; and whenthey havebeen once adjustedthey may continue, in use Without substantial changefor an indefinite period of time. I 1

Heaters in which the heat is developed by current flowing through thefluid itself are best 7 adapted for use with alternating. currents.While direct current may be used, a certain amount of fluid is thenalways decomposed, with the formation of gas and the destruction of thethese objectionable results are not produced in a substantial amount.However, when direct current is used, the amount of fluid decomposed issmall, and if the electrodes are made of mate+ rials which are notaffected by the resulting .conditions, the use of direct current ispractical.

One of the objections to heaters of this type, as heretoforeconstructed, has been the formation of short circuits and the passage ofleakage currents through the water and through the wallsof the heater tothe water pipes themselves. This not only results in a loss of currentbut injuriously affects the pipes as the result of electrolysis, whichoccurs where the current flows between the pipe and the ground. One ofthe objects of my invention is to so connect the heater in theaelectriccircuit as to reduce this leakage current to a negligible amount. v.This object is accomplished by means hereinafter described, theprincipal advantage secured I thereby being the increased safety tolifeand consumed. This object is attained .mainly by 1 the mannerinwhich several groups of conduct ing plates or electrodesare arrangedrelatively to each other and connected into the power circuit, and otherdisconnected electrodes are interposed between members of said groups ofconnected electrodes as will be hereinafter explained.

Referring to theaccompanying drawings which illustrateone form of myinvention: A

Fig. 1 is a View of the heater itself partly in section to illustratethe internal construction;

Fig. 2 is a front view of the connecting panel which is attached toand'forms a part of the heater shownin Fig. 1;

Fig. '3" is a view of two plates of the heater separated to show therelative arrangement thereof;

Fig. 4 is a horizontal section on the line 44', Fig. '1; showing how theheating elements are connected in the circuit.

Fig.6 is a'diagrammatic view of the heating elements and of theelectrical connections therefor.

Heating element The heater proper is built up of a plurality of platesof cast'iron or other suitable material, said plates being all ofthe'same or substantially the same construction and form. These plates,represented by the numerals wand 11 (Fig. 3), have relatively thin bodyportions 12 and thickened rims 13; and the body portions of plates 10are provided in the central portion thereof with perforations 14, whilethe plates 11 have perforations 15 located in the outer portion of thethinner section. The heater is built up of these plates alternatelyarranged, so that, when the thickened edges rest one upon the other thewater is compelled to follow a sinuous path through the heater betweenthe thin body portions of the plates and through the perforations 14 inplates 10 and perforations 15 in plates 11 (see Fig. 5) thereof.

The plates 10 and 11 are separated each from the other by insulatingrings or gaskets 20 which lie between the thickened rims thereof. Therims of the plates are provided on one side with an annular groove orrecess 21, and on the other side with annular recesses 22 (Figs. 1 and3). The gaskets may be made of any suitable insulating material, such asbakelite, rubberized. asbestos, or other suitable insulating material;and as the plates are forced tightly together as hereafter described,the material of these gaskets will be forced into the grooves 21 and 22,thereby aiding in sealing the joints between the plates so that watertight electrically insulated joints may b provided.

The plates 10 and 11 with the gaskets 20 constitute the body of theheater; and the spaces between the plates, in conjunction with theperforations 14 and 15, constitute the sinuous path through which thewater flows. This flow of water may be in either direction, but as hereshown, it will pass in at the bottom and out at the top. Preferably, achamber is formed in the bottom of the heater by the use of rings 30,which are separated from each other and from the heating elements bymeans of insulating gaskets 20 like those used to separate the heatingelements, or by forming an annular rim or header 42.

The heater is completed by headers or plates 40, 42; header 40 beingmounted on the top of the plates and insulated therefrom by a gasket 20,and header 42 being secured to the bottom of the heater, and beinglikewise insulated therefrom by a gasket 20.

The header 40 is provided with an opening into which is secured adischarge pipe 44, while the other header 42 is provided with a pipeinlet 46. And to the latter is secured the main supply pipe 47.

As stated above, the water may flow in either direction through theheater, but as here illustrated it enters through the pipe 47, passesthrough the pipe 46 into the bottom chamber of the heater formed by therings 30, thence through the perforations 15 of the lowermost plate 11,through the annular space between this and the next higher plate 10,thence through the perforations 14 of the last mentioned plate, thencealternately through the outer perforations of the one plate and theinner perforations of the other until the upper end of the heater isreached, whereupon it is discharged from the body of the heater, andpasses out through discharge pipe 51.

The water might discharge from the heater directly into the distributingsystem, but as here shown it discharges into a top chamber made up ofthe annular extension 5'7 of the header 40, which chamber is closed by aremovable cover 48 secured in position by bolts 49, a suitable gasket 50being arranged between the extension 57 and the cover plate 48. Byremoving the bolts 49 and the cover 48, access may be had to the chamberfor any purpose desired.

Clamping devices The plates 10 and 11, and the headers 40 and 42, areheld together by any suitable clamping devices. Those here employed area series of bolts 60 which extend through openings in the headers 40 and42. There may be any suitable number of bolts, but in the form hereshown five are provided. Both ends of these bolts are threaded for thereception of suitable securing devices. Nuts 61 carried by one end ofthe bolts lie against lock washers 62, which in turn rest againstordinary metallic washers 63, and these latter rest upon insulatingwashers 64 lying against the header 42. At the other end, each bolt 60is provided with a similar insulating washer 65, a metallic washer 66above the same, and suitable tension devices. These last mentioneddevices include a helical spring 67 which surrounds the bolt and restsupon the metallic washer 66. Another metallic washer 66 rests upon thetop of the spring, and screwed upon the bolt and resting upon the lastmentioned washer 67 is a nut 68. By screwing down the nut 68 anysuitable tension may be placed upon the spring. This tension must begreat enough to secure the plates together with a pressure sufficient toprevent leakage, while at the same time, the springs allow for normalexpansion and contraction of the heater.

Each bolt 60 is provided at one end with an insulating sleeve or bushing69 which passes through the header 40, and at the other end with asimilar insulating sleeve 69 passing through the corresponding hole inthe header 42. The purpose of these insulating sleeves is to preventloss of electrical energy to the ground and in the heater itself.

To secure the elements of the heater together, the bolts 60 are insertedin the holes in the headers, the bushings 69, and the nuts, washers andsprings are put upon the bolts in their proper order. By tighteningeither or both of the nuts 61 and 68, any desired pressure can beapplied to the springs 67, thereby securing the elements of the heatertogether with the degree of pressure required in each particular case,and yet permitting proper expansion and contraction of the parts.

Casing In the form of the invention here shown, the heating unit issurrounded by a suitable casing consisting of a cylindrical body 70, atop 71 and a bottom 72. the cover plate 48 but contacts with the outsideof the extension or chamber 47. The bottom 72 is provided with anopening through which the pipe 46 extends, and to which the water pipe47 is secured. The top 71 is provided with openings at 73 through whichthe upper ends of the clamping bolts or rods 60 extend, and nuts '74thereon secure the top 71 in position. The outlet pipe 51 extendsthrough a suitable opening in the side of the casing '70, and its innerend is screw- The top '71 does not extend over a may be looked upon as aheat insulating cham- Electrical connections 1 As explainedabove, theplates 10 with their perforations 14, and the plates 11 with theirperforations 15, when piled alternately as described form a sinuousconduit or passageway through which the fluidto be heated is forced toflow, These plates are connected in the circuit in varying combinationsto suit the conditions under which the heater is used. The ohmicresistance of the plates 10 and 11, if madeof iron, is considerable, andtherefore a certain amount of heat is generated in the platesthemselves; thus, while the heating effect is produced primarily in themass of fluid passing through the heater, that heat which is generatedin the plates 10 and 11 due to the resistance thereof, is utilized toraise the temperature of the fluid as it passes through the apparatus.

These plates 10 and 11 may each be provided with a single terminal, orthey may carry any desired number of terminals. In the form hereillustrated, each plate is provided with two terminals 76 arranged atsubstantially opposite points thereon. 1 Theseterminals are connected inparallel so that the plates are supplied with current at a plurality ofpoints. i This is particularly desirable where iron plates are used,be-.

cause of the comparatively high resistance of the material of which theyare composed.

In heaters of this type, as heretofore constructed and when used aswater heaters, there has been an objectionable and serious loss ofcurrent through the water to thepipes which are grounded in the earth.One of the objects of this invention is to reduce this leakage ofcurrent to a minimum, and this is effected in a manner which will now bedescribed. 1

The headers 40 and 42 are of courseconnected to the pipe system of thewater supply and these pipesin use are always grounded. In the ordi-.nary commercial electrical distribution systems, a three wire circuit isused. One of the lines, usually termed the neutral line, leads back tothe generator and isgrounded. There is a difference of potential of 220volts between the two socalled outside or power lines, and a differenceof 110-volts between each of the outside lines and the neutral line.This circuit is well known, and is used with electric ranges and similarappliances. It is well known that-lamps or other apparatus intended tobeused with a difference of potential of 110 volts maybe connected betweeneitheroutside line and the neutral line; and that electrical appliancesintended to be used on 220 volts can be coupled. directly between thesocalled outside lines. p I

Inthe embodiment of my invention'taken for explanation herein,the threew-iredistribution system of 110-220 volts potential isused to illustratethe heater connectionabut myheater can be used on a two wire 110 voltsystem, or on any common distributing system of any potential,

with practically the same results and efliciency.

However, the 110-220 volt system is preferable for domestic use, owingto the smaller wires which may be used to carry the same wattageconsumption.

In my invention, advantage istaken of this common. distribution circuitto so connect the elements of the heater asto limit or reduce to aminimum the leakage of current. .To thistend, theplates wand 11 of theheater. are all insu lated eachfromthe other by the gasketsi20; and theplates are insulated from the headers 40 and 42 by annular gaskets 20,identical, or substantially identical, with the gaskets 20 between theelements. This prevents leakage from the plates 10 and 11 to the headers40 and 42 and thus to ground through a direct metal conductor. Butinasmuch as the current is passing through the fluid. and the fluid ispassing through the pipes of thedistributing system, there is apossibility, in fact a probability, of current leaking through the waterto the grounded pipe, and thence to the ground and through the ground tothe transformer which is always grounded, thus possibly causingelectrolysis where the current passes from the pipe to the ground andvice versa.

To reduce this leakage to a negligible amount, the'plates of the heaterare connected in, the manner shown in Fig. 5, ,tO which reference willnow be made. This figure illustrates the electrodes or plates 10 and 11and the circuits therefor diagrammatically. And for convenience ofreference the several plates are numbered serially from (101) to (119),inclusive. It is to be understood, however, that while 19 plates arehere illustrated, any suitable number may be used; the numbering hereused being employed merely for convenience in describing the circuitconnections.

The top plate 101 is insulated from the header 40, and the bottom plate119 is insulated from the rings 30, which in turn are insulated from theheader 42 by the gaskets 20, as shown in Fig. 1. The plates that arenearest theheaders 40 and 42, that is (101), (119), respectively, areboth connected, as by conductors 142 (Fig. 2), to the neutral, center or110 volt line of the distributing system, which gives them a neutral orsubstantially neutral potential. The outside or 220 volt lines areconnected to certain of the other plates in varying combinations,depending upon the character of the fluid being heated and the amount ofheat it is desired to impart to the fluid, and the amount ofelectricalenergy it is desired to consume over a given period, and otherconsiderations. In the arrangement here shown (Figs. 2, 4 and 5), theone side of the 220 volt line is connected by conductors 141 in multiplewith two heater plates, namely (105) which is near the top thereof, and(113) which'is near the middle thereof; and the other 220 volt line is.similarly connected by conductors 141 with the plate (109) near themiddle of the heater and with the plate (116) near the bottom thereof.But these particular connections are-illustrative only, and variousother combinations may be employed.

By these connections, it will be noticed that while the plates (101) and(119) are of neutral or nearly neutral potential, there will be adifference of potential of 110 volts between the top plate (101) and theplate (105), and between the bottom plate 119) and the plate (116); andunder this difference of potential a certain amount of current willflow, depending upon the resistance of the fluid being heated. Byvarying .the number of intervening Plates and the length of the liquidpath, this resistance may be varied at will, and consequently the amountof current also varied as required by the conditions of any particularsituation. Under this difference of potential, a certain limited amountof current will flow between plates.

(101) and (105) at the top, and plates (116) and (119) at the bottom;but there will belittle tendency for current to flow from the end platesto ground, as the resistance of the wire or wires connected to plates(101) and. (119) and thence direct to the transformer will always beconsiderably less than the total resistance of the rings 30, the headers40 and 42, the pipes 44, 46 and 47 and the liquid contained therein. Butwhile there is a difference of only 110 volts between the groups ofplates just referred-to, there is a difference of 220 volts betweenother groups of plates; for instance, there is a difference of 220 voltsbetween plates (105) and (109) and between the plates (109) and (113);and between plates (113) and (116). Inasmuch as the voltage between thelast mentioned groups is double that between the upper and thelowergroups, the tendency of the current will be to flow between these plates(105) to (116) rather than between plates (101) to (105) and (116) to(119); or between the individual plates (101) and (119) to the ground,as represented by the inlet and outlet pipes connected to the heater. Bythus providing for the maintenance of potential differences of variousdegrees in different parts of the heater a substantial gain ineffioiency is accomplished as pointed out herein' after. 7 1

1 In the particular arrangement here shown, the fluid is supposed toenter at the bottom and pass out at the top of the heater, although thecirculation may be in the reverse direction if desired. Most fluids whencold normally have a higher resistance than when heated; therefore, asmaller number of unconnected plates are shown between the connectedones at the bottom of the heater, than there are unconnected plates atthe top of the heater, where the fluid has become heated.

By using a large number of plates, and coupling these in circuit asdemanded bythe circumstances, it is possible to adapt heaters of thiskind to widely varying conditions; it being merely necessary todetermine by test the best combination for any particular heater orparticular location, temperature of, or quantity of heated fluiddesired, and then couple in the plates in accordance with therequirements of that situation, and the requirements of the user as tothe desired temperature of the fluid and wat tage consumption.

The plates, conductors or electrodes 10 and 11 may be connected incircuit in any suitable way. As here shown, the heater casing carries onone side thereof a terminal box and coupling devices for connecting theplates in circuit as desired. These parts are shown in section in Fig. 1and in front View in Fig. 2.

Referring more particularly to this feature, the casing '70, Figs. 1 and4, has secured thereto a board or panel 130 of insulating material bymeans of bolts 131. Mounted on the board or panel 130 is another boardor panel 132 of insulating material, and upon this last mentioned boardor panel are three conducting strips or bus bars 133, 134, 135 (Fig. 2),which are terminals respectively of the three wires of the distributingcircuit. Bus bars 133, 135 are the terminals of the two 220 volt wires,respectively, and 134 is the terminal of the neutral wire. These barshave secured therein suitable binding posts 138; and the insulatingpanel 132 carries a number of binding posts 139, one

plained before, this is merely illustrative, and a much larger numbermay be used.

All of the binding posts on panel 132 are indicated by the numerals 139;but in Fig. 2, those particular binding posts which are selected for usewith the plates of this heater are also numbered with the numbers of theseveral plates, as shown in Fig. 5, so that the several circuits may bemore easily traced. Thus the post 139 which is connected to plate 101 ismarked (101); that connected to plate 105 is marked (105); thatconnected to plate 109, as (109); and so forth throughout the series. Infact, all of the plates'of the heater are in practice preferablyconnected to the correspondingly numbered binding posts 139, so that anyconnections necessary can be readily made.

Each of the series of plates 10, 11, is connected by a conductor 140 toone of the series of binding posts 139. As shown in Fig. 4, theseconductors 140 are carried into the heater from panel 132 through anopening 150 in casing 70. Three of said conductors 140 are there shown,each connected with two binding posts 76 in the rim (preferablydiametrically opposite each other) of one of the plates. Each of saidplates 10, 11, is similarly connected with its own binding post on panel132.

Conductors 141 (Fig. 2) connect certain of the binding posts 139 and theelectrodes connected thereto, these being selected as herein indicatedaccording to the local conditions and requirements, with one or theother of the terminal bars 133, 135 of the 220 volt lines of thethree-wire power circuit; conductors 142 connect other binding posts andelectrodes, selected according to the same conditions and requirements,with the terminal 134 of the neutral or 110 volt line. By means of theseterminals and circuit connections, as shown more in detail in Fig. 2, itis possible to connect the heating plates or electrodes in variousgroupings or combinations with the power circuit, so as to obtain ineach case the particular variation of potential differences in differentparts of the heater that are best suited to the local requirements.

It is impossible to show all of the circuit connections in, Figs. 1 and4; but a clear understanding thereof may be had by referring to Figs. 2and 5, which, for convenience of description, may be consideredtogether; Fig. 2 representing the terminal board or panel, and Fig. 5the plates in diagram. The connections are indicated for theparticularheating plates selected for de scription in this specification, it beingunderstood that these connections may be varied at will.

Conductors 140 connect the top plate (101) and bottom plate (119) of theheater with binding posts 139 on the terminal board 132, and these inturn are connected by connectors 142 to the neutral or 110 volt bus bar134; and the other plates (10.5), (109). (113), and (116) are connectedby other wires 140 to their respective binding posts 139 on terminalboard or panel 132, and thence by connectors 141 to the binding posts138 on one or the other of the 220 volt bus bars 133 or 135, as may bedesired. In this instance plates (105) and (113) are shown connected tobar 133, and plates (109) and (116) to bar 135.

Assuming the parts to be connected as shown, current will flow betweenthe several plates connected directly to the two sides of the 220 voltlines.

For instance, current will flow from the 220 volt line connected to bar133, through the connections 141 to the binding posts 139 and (113) onboard or panel 132, thence through conductors 140 to the plate (.105)and (113) in parallel, through the heater to the plates (109,) and(116), through other conductors 140 back to binding posts 139 (10.9) and(1.16.) on board or panel 132, through connectors .141 to the bar to theother side of the 220 volt line.

With the active plates referred to connected to the opposite sides ofthe 220 volt circuit, and the end plates (101) and (119) connected tothe neutral line, the tendency is for the current to pass between theplates having the greatest difierence of potential; so that, as in allthree wire distributing circuits, no current or substantially nocurrent, will pass through the neutral line; but the end plates 101) and(119) are connected to the neutral line so that stray currents, orcurrents due to an unbalanced condition of the system, will make circuitthrough the end plates (101) and (119), through their respectiveconductors 140, to their binding posts 139- (101) 139 (119), connectors142, to bus bar 134, which is connected through the neutral line to thetransformer.

The plates (101) and (119) and the headers 40 and 42 are always atneutral potential, therefore there is no diflerence of potential betweenthe plates and the headers, and therefore there is no tendency forcurrent to pass from plates to the headers, and thence through the pipesto the ground. Thus these end plates connected in this manner andinsulated from the headers, act as screens to prevent the flow ofcurrent into the pipe system and to ground.

As explained above, not all the plates 10 and 11 are usually in circuitat the same time, and the unconnected platesare merely idle plates,considered strictly as electrodes. They nevertheless serve an importantpurpose, whereby the efliciency of the heater is substantiallyincreased; for as the current passes between the active plates it willflow partly through the liquid" in the heater and partly through the.intervening plates. There being a continuousliquid path through theholes 14 and 15, part of the current will take this path, whileanotherportion .will pass from the active plates directly through the liquid tothe next adjacent plates, thence from plate to liquid and liquid toplate to the next active plate.

By means of the above described construction and circuit connections,advantage is taken of the fact that when current passes from one mediumto another, as from solid-to liquid and vice versa, there is always adefinite fall of potential and a consequent dissipation of energy at thepoint of transit. In a heater constructed according to the presentinvention such a fall of potential takes place at several points, theenergy thereby generated being transformed into heat, which is absorbedby the liquid passing throughthe heater. It has been found inpracticethat a heater thus constructed iscons iderably more eiiicient than onein which the current is forced to now 1 through the fluid only, orthrough a resistance element only.

Having thus described my invention, what I claim is:- 1

1. In an electric heating system, the combination of a plurality ofelectrodes, means for circulating the substance to be heated between thesame, means for insulating the electrodes from the system, means formaintaining the ends of the heater at low or zero potential; and meansfor passing current between the electrodes at any desired rate withinthe capacity of the generator and through any desired section orsections of the heater. 1

v2. In an electric heater, the combination of a plurality of electrodesbetween which the medium to be heated may flow, means for connecting theelectrodes near the ends to the neutral line of a three wiredistributing system, and means for connecting intervening electrodes tothe other lines of the system.

3. In an electric heater, the combination of a plurality of platesspaced apart and having openings therein so that when secured together atortuous path for the flow of fluid is provided, means for insulatingthe plates each from the other, means for maintaining the plates nearthe end of the heater at or near zero potential, means for maintainingthe other plates at different potentials so that current will flowthrough the heater between the last mentioned plates.

4. In an electric heater, the combination of a plurality of platesspaced apart and having openings therein so that when secured together atortuous path for the flow of fluid is provided, means for insulatingthe plates each from the other, means for maintaining the end plates atlow or zero potential, means for maintaining a definite but variablepotential difference between certain of the other plates and the endplates, and means for maintaining a definite but variable and greaterpotential difierence between the other plates of the heater.

5. In a water heating system, the combination of a supply pipe and adischarge pipe, a heater comprising a plurality of plates between whichthe water may flow located between the supply and discharge pipes, meansfor insulating the' plates from each other, means for insulating theheater from the supply and discharge pipes, means for maintaining theends of the heater at neutral potential, and means for maintaining otherof the plates at substantial potential.

6. In a water heating system, the combination 120 of a supply pipe and adischarge pipe, a heater comprising a plurality of plates between whichthe water may flow located between the supply and discharge pipes, meansfor insulating the plates from each other, means for insulating theheater from the supply and discharge pipes, means for connecting theends of the heater with a source of neutral potential, and means forconnecting other of the plates with a source' of higher potential. 7. masubmerged type of electric heater, the combination of a plurality ofplates or electrodes insulated from each other, a terminal board, andmeans for connecting the plates or electrodes in sections or groups withthe terminals of the 5 board, so that in each section or group there maybe maintained a definite but variable wattage consumption for eachsection or group independently of the others.

8. In a submerged type of electric heater, the combination of aplurality of plates or electrodes insulated from each other, a terminalboard, and means 'for connecting the plates or electrodes with theterminals of the board so as to maintain any predetermined temperaturein the material being heated irrespective of the conductivity thereof.

9. In a submerged type of electric heater, the combination of aplurality of plates or electrodes insulated from each other, a terminalboard, and 15c means for connecting the plates or electrodes with theterminals of the board so that the plates may be variably connected incircuit to maintain a given wattage consumption whatever theconductivity of the material being heated may be.

10. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage between theelectrodes for the flow of the liquid to be heated; means for connectingthe end electrodes of those which are connected to circuit to theneutral line of a supply circuit; and means for connecting an electrodeintermediate of said end electrodes to a power line of the supplycircuit.

11. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage between theelectrodes for the flow of the liquid to be heated; means for connectingthe end electrodes of those which are connected to circuit to theneutral line of a supply circuit; and means for connecting two or moreelectrodes intermediate of said end electrodes each to a power line ofthe circuit.

12. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage between theelectrodes for the flow of the liquid to be heated; means for connectingthe end electrodes of those which are connected to circuit to theneutral line of a supply circuit; means for connecting two or moreelectrodes which are intermediate of said end electrode to a power lineof said supply circuit; and means for connecting two or more otherelectrodes which are intermediate of said end electrodes to another lineof said supply circuit, said intermediate electrodes which are connectedto one line alternating with said interme diate electrodes which areconnected to the other line.

13. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage between theelectrodes for the flow of the'liquid to be heated; means for connectingthe end electrodes of those which are connected to circuit to theneutral line of a three-wire supply circuit; means for connecting anelectrode intermediate of said end electrodes to one of the power linesof said supply circuit; and means for connecting another electrodeintermediate of said end electrodes to the other power line of saidsupply circuit.

14. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage between theelectrodes for the flow of the liquid to be heated; means for connectingthe end electrodes of those which are connected to circuit to theneutral line of a three-wire supply circuit; means for connecti ing twoelectrodes intermediate of said end electrodes to one of the power linesof said supply circuit; and means for connecting another electrodeintermediate of said two electrodes to the other power line of saidsupply circuit.

15. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage between theelectrodes for the flow of the liquid to be heated; means for connectingthe end electrodes of those I. which are connected to circuit to theneutral line of a three-wire supply circuit; means for connecting two ormore electrodes which are intermediate of said end electrodes to one ofthe power lines of said supply circuit; and means for connecting two ormore other electrodes which are intermediate of said end electrodes tothe other power line of said supply circuit, said electrodes which areconnected to one power line alternating with said electrodes which areconnected to the other power line.

16. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage between theelectrodes for the flow of the liquid to be heated; means for connectingone end electrode of those which are connected to circuit to the neutralline of a three-wire supply circuit; means for connecting anotherelectrode to one of the power lines of said supply circuit; and meansfor connecting another electrode to the other power line of said supplycircuit.

1'7. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage between theelectrodes for the flow of the liquid to be heated; means for connectingone end electrode of those which are connected to circuit to the neutralline of said supply circuit; means for connecting two or more otherelectrodes to one of the power lines of said supply circuit; and meansfor connecting two or more other electrodes to the other power line ofsaid supply circuit, said electrodes connected to one power linealternating with said electrodes connected to the other power line.

18. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage for theflow of the liquid to be heated; means connecting certain selectedelectrodes with the power lines of a three-wire supply circuit; andmeans connecting one of the end electrodes of those connected to circuitwith the neutral line of said supply circuit.

19. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage for theflow of the liquid to be heated; means connecting certain selectedelectrodes with the power lines of a three-wire supply circuit; andmeans connecting the last electrode of those connected to circuit at thehot end of the heater with the neutral line of said supply circuit.

20. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage for theflow of the liquid to be heated; means for connecting certain selectedelectrodes with the power lines of a three-wire supply circuit; andmeans for connecting the end electrode of those connected to circuitwith the neutral line of said supply circuit.

21. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage between theelectrodes for the flow of the liquid to be heated; means for connectingone of said electrodes to one line of a supply circuit; means forconnecting another of said electrodes to another line of said supplycircuit, there being interposed between said electrodes one or moreelectrodes which are not connected to said supply circuit.

22. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage between theelectrodes for the flow of the liquid to be heated; means for connectinga plurality of said electrodes to one line of a supply circuit; meansfor connecting another plurality of said electrodes with another line ofsaid supply circuit, the electrodes connected with the two lines of thesupply circuit alternating with each other, and there being others ofsaid electrodes not connected to the supply circuit and interposedbetween some or all of said electrodes which are connected to the supplycircuit.

23. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage for theflow of the liquid to be heated; means for connecting certain selectedelectrodes with circuit conductors of different potential; and one ormore unconnected electrodes interposed between said connectedelectrodes.

24. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage for theflow of the liquid to be heated; means for connecting certain selectedelectrodes with circuit conductors of different potential; means formaintaining the end electrodes of those connected to circuit at low orzero potential, and one or more unconnected electrodes interposedbetween said connected electrodes.

25. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage for theflow of the liquid to be heated; means for connecting certain selectedelectrodes with circuit conductors of difierent potential; means formaintaining one of the end electrodes of those connected to circuit atlow or zero potential, and unconnected electrodes interposed betweensaid connected electrodes.

26. In an electric heater, the combination of a plurality of electrodesinsulated from each other and spaced apart to form a passage for theflow of the liquid to be heated; means for connecting certain selectedelectrodes with circuit conductors of different potential; means formaintaining the end electrodes of those connected to circuit at low orzero potential; an unconnected electrode or electrodes interposedbetween the electrodes of said connected group; and other unconnectedelectrodes interposed between the group of connected electrodes and eachof said end electrodes.

GEORGE NORRELL SEXTON.

